1. Field of the Invention
The present invention relates generally to a connector for connecting a comparatively thin resin tube of a diameter less than about 40 mm to be used as an oiling or air supply path of an automobile or various kinds of machines and devices and more particularly to the structure of a small-diameter resin tube connector.
2. Description of Prior Art
Conventionally, various kinds of quick-connectors for connecting small-diameter tubes have been proposed and put to practical use. One example of them has the following structure. That is, as shown in FIG. 5, this connector comprises a cylindrical main body 21 which is provided with a small-diameter chamber 23-1 and a large-diameter chamber 23 which are continuous with a communication hole 24 defined by a flexible hose connecting cylindrical wall 22 at the top of the main body 21 and a separate socket 28 having a plurality of pawl walls 25 which are inwardly inclined toward the front portion of the outer peripheral wall defining an axial central hole. Further, the small-diameter chamber 23-1 has seal rings 26 and bushes 27 disposed therein and the large-diameter chamber 23 is provided with an engagement hole 21-1 drilled through the outer peripheral wall with the formation of a support wall 21-2 at the rear end thereof. The mechanism of the connector is such that the annular peripheral wall 25-2 of the rear end of the socket 28 is fitted into the connector main body 21 while the shoulder 25-1 of the base portion of each of the pawl walls 25 is held engaged with the edge of the engagement hole 21-1 whereby the pawl walls 25 of the socket 28 is brought into pressure-engagement with an annular bulged wall P0xe2x80x2 of a tube P0 assembled into the main body 21 in advance thereby connecting the tube P0 to the connector.
As another example of such quick connector, there is a connector which is proposed by the present applicant and which is disclosed in the Japanese Unexamined Patent Publication No.H9-280451/1997(Japanese Patent Application No.H8-121063/1996). This connector has the following structure. That is, the connector has a main body provided a small-diameter chamber and a large-diameter chamber both of which are formed by expanding a communication hole extending through the connecting cylindrical wall of the flexible tube connecting end of the main body. The small-diameter chamber has seal rings and bushes disposed therein and the large-diameter chamber is provided with recessed windows formed through the outer peripheral wall of the chamber in opposite relationship with each other. Further, a socket having inwardly energized repulsive walls each in the form of a pawl wall projecting forward and including an inwardly-inclined intermediate portion and a projected wall extending over the outer periphery of the connector main body is formed integral with the connector main body whereby a tube is connected to the connector by bringing the repulsive walls into pressure-engagement with the annular bulged portion of the tube.
However, these conventional techniques have had the disadvantage that although no problem arises when the tube assembled into the connector is made of a metallic material since the annular bulged wall formed near the connecting end of the tube has a sufficient degree of mechanical strength, when the tube is made of a flexible resin material such as a polyamide type resin material and has an annular bulged wall formed by press working in the axial direction under a heated condition or by several steps of press working in the axial direction at the normal temperature, if a draw-out force is applied on the tube, even when the tube is made of a hard polyamide type resin not mixed with a plasticizer, the mechanical strength of the tube against the draw-out force is not sufficient so that the annular bulged wall becomes deformed to get out of engagement with the pawl walls or the repulsive walls of the socket and the tube is sometimes drawn out from the connector.
As a means for eliminating the above-described problem, there is a bite type small-diameter pipe connector as shown in FIG. 6. Such type of connector comprises a main body 31 including a small-diameter chamber 33xe2x80x2 attached with a cylindrical insert 34 and having a seal ring 35 and a collet 36 having at the rear end thereof an inwardly inclined pawl wall 36xe2x80x2 whose outer peripheral surface forms a projecting wall, a large-diameter chamber 33 having a stopper 37 attached thereto and a releasing member 38 capable of moving in the axial direction of the main body 31. With such an arrangement, when a resin tube P0xe2x80x2 is inserted into the connector and then moved rearward, the tube comes into engagement with the stopper 37 at the projecting wall of the collet 36 so that the pawl wall 36xe2x80x2 of the collet 36 is caused to bite into the outer peripheral surface of the tube while when such biting is desired to be released, the releasing member 38 may be pushed forward in the axial direction from outside.
However, such bite type small-diameter tube connector has the disadvantage that although it is resistant against the draw-out force applied to the resin tube P0xe2x80x2, when a strong draw-out force is applied on the resin tube, the pawl wall 36xe2x80x2 of the collet 36 comes to bite too deep into the tube which sometimes results in breaking the resin tube and further, since the stopper 37, the collet 36 and the releasing member 38 are disposed within the connector main body 31, the collector main body can not but become large-sized in the radial direction and as a result, the overall size of the product is forced to become large-sized failing to comply with the recent miniaturization requirement so that means for improving such connector has long been awaited.
The present invention has been made in view of the current state of tube connection by the small-diameter resin tube connecting structure used for the above-described conventional small-diameter tube connector.
Accordingly, an object of the present invention is to provide a small-diameter resin tube connecting structure for a small-diameter tube connector which connecting structure can securely maintain a favorable connecting condition for a prolonged period of time even when a conventional small diameter tube connecting quick connector is used as it is, can increase its resistance against a tube draw-out force applied on the connector, can manufacture easily and in a simple manner without the necessity of making the connector large-sized.
In order to achieve the above-described object of the invention, the invention provides a small-diameter tube connector comprising a main body including therein a small-diameter chamber formed by expanding a communication hole defined by a connecting cylindrical wall at the top end of the main body and having seal rings and bushes disposed therein, a large-diameter chamber formed in the same manner as the small-diameter chamber and having engagement holes or recessed windows formed through the outer peripheral wall thereof in opposite relationship with each other, a socket formed integrally with, or separately from, the main body of the connector and having inwardly energized repulsive walls at the engagement holes or the recessed windows, respectively, each being in the form of a pawl wall whereby the repulsive walls are brought into engagement with an annular bulged wall to be formed on the outer peripheral surface of a target resin tube to be connected. The characteristics of the invention reside with a small-diameter resin tube connecting structure in which a thin-wall metallic tube having an annular bulged wall portion is inserted into at least the connecting end of the resin tube with the metallic tube serving as a reinforcing member and also resides with the formation of an annular bulged wall on the outer peripheral surface of the resin tube by press-working the metallic tube in the axial direction.